Chronic post-thoracotomy pain is the most common long-term complication that occurs after a thoracotomy with a reported incidence of up to 80%. While thoracic epidural analgesia has become the mainstay for managing acute post-thoracotomy pain, its effect on the chronic post-thoracotomy pain seems questionable. The objective of this prospective, double-blinded, randomized, controlled trial was to assess the effect of preemptive low-dose epidural ketamine in addition to preemptive thoracic epidural analgesia on the incidence of chronic post-thoracotomy pain.